Research On Composite Generation And Transmission System Reliability EvaluationAlgorithm For Megalopolis

With the development of social and economic and the rapid increase of urbanizationlevel, the number and the scale of the big cities are expanding rapidly. The increasing ofthe electricity demand and the quality demand, and the complexity of urban power gridbring a higher demand on composite system reliability evaluation for big city. Compositesystem reliability calculation includes state selection, state evaluation and indexcalculation. State evaluation mainly includes power flow calculation and overloadadjustment, and it is the main factor that affects the reliability calculation speed and thekey that whether the reliability evaluation algorithm can be applied to large-scalecomposite system or not.To resolve conflicts between power flow calculation speed, scale and precision incomposite generation and transmission system reliability evaluation and the pooradaptability of the power flow model in actual system, PSD-BPA is used to calculatepower flow. The load-bearing capacity of the line is decided by its safe carrying capacity.By using line current constraint to decide if the line is overloaded instead of capacityconstraint, the results are more accurate. Considering the engineering practicability, thelocal load shedding model is used. The output regulation of units is the first priority. Theover-cut of load is adjusted to find the best load cut that the line is just not overloaded.Based on the thought and method mentioned above, the flow charts of the compositesystem static reliability evaluation algorithm which can be used for megalopolis aregiven in this thesis, so are the flow charts of the software design. A probabilisticreliability evaluation program is developed with the calling of PSD-BPA. It can reducethe manual workload by using this software to evaluate the system reliability. Data-in ofthis software is flexible, using BPA power flow form. Output of this software is detailedand visual, providing not only the probabilistic reliability indices of the system, elementand load, but also the detailed power adjustment process for reference by user. Variousmeasures are taken to alleviate the heavy computation caused by the large amount ofcontingency states of state enumeration, so the efficiency and the practical of thesoftware are improved.IEEE-RTS79reliability test system and some actual power grids have been tested bythe software, and the evaluation results show that the algorithm is of effectiveness andavailability.